1. Field of the Invention
The present invention relates to a technique of reproducing moving image data.
2. Description of the Related Art
Recently, the use of high-speed Internet connection services and wired and wireless home networks has rapidly become popular. A use method has becoming popular, which stores moving image contents converted into digital data in a home server to allow the user to view the contents on another device through a home network or receives moving image contents from a moving image distribution service on the Internet and allowing the user to view the contents. Even when a user is away from home, he/she can view moving image contents by transferring the contents to a portable reproducing device through the Internet. In order to allow a user to comfortably view these moving images, it is desired to start reproducing a moving image content immediately after the user issues a view instruction by operating the reproducing device as well as to display moving images actually reproduced and displayed with high image quality.
When downloading a moving image content on a network and reproducing it, the reproducing device starts reproducing it with a delay corresponding to the time required for data transfer with respect to when a moving image content held as a local file. In order to eliminate such a delay of the start of reproduction, a reproducing device performs streaming reproduction, i.e., storing, in the buffer of the reproducing device, moving image data in an amount that allows partial reproduction without waiting for the transfer of all the data of the moving image content, decoding the stored moving image data, and reproducing it.
Streaming reproduction makes it possible to seamlessly reproduce moving image data while hiding the time required for data transfer by decoding and reproducing partial moving image data and concurrently transferring partial moving image data to be reproduced next. In addition, even a portable reproducing device with a small storage capacity can perform streaming reproduction because it need not hold all moving image data of a large data capacity at once by using, for example, a method of discarding reproduced partial moving image data at proper timing.
As a conventional technique associated with streaming reproduction, for example, the technique disclosed in Japanese Patent Laid-Open No. 2004-080145 is available.
With regard to the first part of a moving image content to be started to be reproduced, however, reproduction cannot hide the time required for data transfer, and hence there is still a wait time between the instant at which the user issues a reproduction instruction and the instant at which reproduction starts.
The data transfer time greatly depends on the data transfer rate of a network to be used, an encoding scheme for a moving image content to be transferred, and a code amount per unit time. Recently, with the proliferation of high-speed Internet and high-speed wireless communication schemes, the data transfer rate has increased year by year. At the same time, however, the resolution and data transfer rate of moving image contents to be viewed have increased. In addition, the number of users has increased. Increases in resolution and transfer rate will cause not only increases in the congestion of the network and server load but also increases in the amount of transfer data stored until the start of reproduction. In addition, an increase in the number of users will increase the congestion of the network and the processing load on servers.
An increase in the speed of a network therefore is effective only in a use condition where the use of the network can be widely ensured, and hence provides no method of solving problems associated with the transfer and reproduction of the moving image data of moving image contents.
The present invention has been made in consideration of the problems in the prior art, and has as its object to provide a video reproduction technique which can shorten the time required for the start of reproduction of moving image data.